On the first day of Dr. Martin MacNeill's murder trial, prosecutors painted the former Mormon Sunday school teacher as a liar who was hell-bent on making his wife have a facelift so he could poison her with a lethal cocktail of drugs during her recovery.

The motive, prosecutors said, was a woman named Gypsy Willis, who MacNeill had met online more than a year and a half before he allegedly killed his wife, Michele MacNeill, in April 2007.

Days after MacNeill's facelift surgery, she was found by her 6-year-old daughter slumped over in a bathtub. Less than two hours later, the mother of eight and former beauty queen was pronounced dead.

Deputy Utah County Attorney Sam Pead said during opening statements today that MacNeill, 58, acted erratically around the time of his wife's death and said she was the one who wanted the surgery.

"Why did she have the surgery? ... Why did she take all of those medications? I told her not to do it. I'm a doctor. She's dead. I've been a bishop. I pay tithing, and this is the way you repay me?" MacNeill yelled in front of first responders, according to Pead.

MacNeill also told inmates after his arrest that his wife was a "b----," that he was glad she was dead and that authorities would never be able to prove he killed her, according to Pead.

The medical examiner has never determined a cause of death.

Defense attorney Susanne Gustin told the jury that heart disease was the "cause or contributing cause" to MacNeill's death. She conceded during open statements that "Martin has made poor choices in his life. We've heard he had affairs during his marriage."

"We may think he is a total jerk, that is absolutely disgusting and that's natural. But it's very critical that during this trial you set aside your emotion," she admonished the jury.

Dr. Scott Thompson, the plastic surgeon who performed MacNeill's facelift, was the first witness called to testify today by the prosecution.

Thompson said he prescribed more drugs than usual to MacNeill at the request of her husband. He said he felt comfortable doing so "because Martin was a physician and he asked me for these things."

A jury of eight people in Provo, Utah, will decide the doctor's fate in a trial that is expected to last five weeks and pit MacNeill against his daughters, who are expected to be star witnesses for the prosecution.

One of them is Ada MacNeill, now 12 years old. Two of MacNeill's other daughters, Alexis Somers and Rachel MacNeill, are also expected to take the stand. Both have consistently been a presence in the courtroom during pre-trial hearings, often clutching pictures of their mother as they glared at their father.

"He had a plan to murder my mother, and this was just part of his plan," Somers told ABC News in 2012.

While caring for her mother after the surgery, Somers said, her mother made an ominous statement.

"A few days before her death, I was helping her wash her hair and she turned to me and said, 'Alex, if anything happens to me, make sure it was not your father,'" Somers said.

The jury is also expected to hear from MacNeill's alleged mistress, who moved into the family's home as a nanny weeks after Michele MacNeill's death.

Martin MacNeill also served three years in a Texas federal prison for fraud and was released in July 2012.